I like the delayed effective fighter level progression. With the changes you made there, do you think it's usable?

As for your Eldritch Blast conundrum, (2) is a workable solution, but the increasing fortification and change of creature type are kind of huge mechanical things to try and refluff. I mean, the idea of turning into an eldritch being of pure dark magic is pretty awesome, and could be noted as an adaptation option with the Savant even if you go with the other solution, but it doesn't quite work if a player just wants to be a warlock who's picked up a few martial maneuvers, you know?

I think it would be best to go with (1) and just add a note that says, "look, there are some horrible tricks you can pull with this, so I recommend not allowing your players to take Eldritch Glaive."